Development of naturally occurring siliceous material for the preferential removal of thorium from U–Th from aquatic environment

Abstract

During this work highly particle reactive nature of thorium was exploited for the separation of Th from aquatic stream containing U/Th. The Kd value of Th(IV) ions is 106 which is two order of magnitude higher than uranium (IV & VI). Laboratory simulated experiments were conducted to study the preferential removal of thorium by using siliceous material having particle size of about 2,000 μm. Siliceous material was prepared by decomposing the organic layer on soil particles by giving treatment with HNO3 and H2O2. Experimental solutions were generated by spiking the surface water with Th (NO3)4 and UO2(NO3)2. Experimental results shows preferential uptake of Th compared to U by siliceous material. This association is further improved by coating the siliceous material with high and low molecular weight organic materials i.e. humic and fulvic acid, respectively. Characterization of the organic material was done by ATR–FTIR whereas determination of Th was done by ICP-OES and alpha spectrometry. Experimental results clearly showed that Th and U sorption capacity is 1 and 0.3 μg mg−1 (w/w), respectively, in case of siliceous material. Thorium sorption is increased five and eight times in the case of coating with fulvic acid and humic acid, respectively. Whereas the same does not shows any pronounced impact on sorption of uranium.